Return reference to a vector member variable

Question

I have a vector as member in a class and I want to return a reference to it through a getVector() function, so as to be able to modify it later. Isn’t it better practice the fun

Answer 1

it's not unusual to declare both const and mutable variants, like so:

std::vector& VectorHolder::getVector() {
  return myVector;
}
const std::vector& VectorHolder::getVector() const {
  return myVector;
}

the underlying problem with your program is that you return a non-const reference from a const method.

std::vector& VectorHolder::getVector() const {
  return myVector; // << error: return mutable reference from const method
}

so you make it const using this form:

const std::vector& VectorHolder::getVector() const {
  return myVector; // << ok
}

and when this is in a non const method or the client holds a non-const reference, then you can legally use a non-const method:

std::vector& VectorHolder::getVector() {
  return myVector; // << ok
}

finally, you could return a value (in some cases):

std::vector VectorHolder::getVector() const {
  return myVector; // << ok
}

because the copy requires no mutation and provides no exposure to the internal data.

so you will end up declaring both variants quite often.

the results of declaring both are:

VectorHolder m;
const VectorHolder c;

m.getVector().size(); // << ok
c.getVector().size(); // << ok - no mutation

m.getVector().push_back(a); // << ok
c.getVector().push_back(a); // << error: attempt to mutate const reference because the const vector is returned

so it all works out nicely (apart from the redundancy of the methods).